The Future of Energy Storage — ‘Sisyphus Railroad’

In research there is evolution, revolution and — sometimes — what I call “retro revolution,” which happens when old methods have new applications. All three are in play in the world of electricity, and are affecting storage.

The inability to store electricity has been a challenge since the time of Thomas Edison. Electricity is made and used in real time, putting huge pressure on utilities at particular times of the day. For much of the East Coast in summer, for example, the peak is in the evening, when people come home from work or play, crank up the air conditioning, flip on the lights, the TV and start cooking. In many cities, the subways operate at peak and the electricity supply is stretched.

Traditionally, there have been two ways to deal with this. One is that utilities have some plant on standby, in what is called “spinning reserve,” or they have gas turbines ready to fire up.

Solar and wind power, an increasing source of new generation, have made the need to store and retrieve power quickly more critical. The sun sets too early and the wind blows willy-nilly. Also the quality of the power reaching the grid varies in seconds, necessitating a quick response to ease supply or increase it.

Until now, the best way to store large amounts of electricity — it is never really stored, but has to be generated afresh — is known as “pump storage.” This occurs when water is pumped up a hill during low demand times, at night and early in the morning, and released through generators to make new electricity during peaks.

It has gotten harder and harder to get permission to install new pumped storage because the best locations are often in scenic places. In 1962, Consolidated Edison Co. proposed building a pump storage facility on the Hudson River at Storm King Mountain near Cornwall, N.Y. After 17 years of environmental opposition, it gave up.

Now battery technology has reached a point where utilities are installing banks of lithium-ion batteries to help with peak demand. They also play an important part in smoothing out variable nature of alternative energy.

Batteries are not the only play, but because Mr. Battery, entrepreneur Elon Musk, is a showman, they tend to get more public attention.

Other mechanical methods hold as much promise and some dangers. One is flywheels, which would be wound up at night and would release power when needed. It is an old concept, but one that has new proponents — although there are concerns about when things go wrong and that super-energetic device flies apart.

“What happens if it gets loose and goes to town?” asks a wag.

Another method is compressed air in underground vaults. Natural gas already is compressed routinely for storage. The technology exists, but the compression would have to be many times greater for air, and there are concerns about the impact of this “air bomb.”

Yet another method involves a column of water with a heavy, concrete weight pressing down on it.

My own favorite — and one likely to appeal to many because of its safety and mechanical efficiency — is an electric train that stores energy by running up a track and then down to generate power. A Santa Barbara, Calif. company, Advanced Rail Energy Storage (ARES), is planning to run a special train 3,000 feet up a mountain track in Pahrump, Nev., and then have the train come down the mountain, making electricity as it does so. They plan to use hopper cars loaded with rock or other heavy objects. The Economist magazine has dubbed it the “Sisyphus Railroad.”

The train will go up or down the track depending on the needs of the California grid to which it will be linked. The developers claim an incredible 85-percent efficiency, according to Francesca Cava, an ARES spokeswoman. “That’s what you get with steel wheels on steel track,” she says.

The company has received Bureau of Land Management approval for its 5.5-mile track, and construction of the energy train starts next year. “All aboard the Voltage Express making stops at Solar Junction, Wind Crossing and Heavy Goods Terminal.”

Comments

It is a fact that the gravitational potential energy (with respect to sea level) of the water in Lake Titicaca, which is a lake high in the South American Andes, bordering Peru and Bolivia, is greater than the entire electrical energy generated in the United States in a whole year.

Nature has demonstrated what is possible and should inspire mankind to be ambitious in our pumped hydroelectric energy storage engineering elsewhere in the world.

Admittedly, not every country is blessed with mountains as high as the Andes in which to build hydroelectric reservoirs.

Nevertheless, even with lesser mountains or highlands, much can be achieved. I have designed a pumped-storage hydro-scheme for the Scottish Highlands, the Strathdearn Pumped-Hydro Scheme – which could store up to 6,800 GWh, more than enough capacity for all of Britain’s energy storage needs!

I came across your interesting article regarding energy storage technologies. As a pumped storage developer, I am writing to address some of the assumptions and conclusions apparent in the piece.

First, your note on pumped storage siting is misleading. You wrote:

“It has gotten harder and harder to get permission to install new pumped storage because the best locations are often in scenic places. In 1962, Consolidated Edison Co. proposed building a pump storage facility on the Hudson River at Storm King Mountain near Cornwall, N.Y. After 17 years of environmental opposition, it gave up.”

This was indeed one of the highest profile failures of a pumped storage proposal, but it is not representative of the majority of projects proposed today. There were more than 30 pumped storage projects built in the US between the 1950’s through the early 1990’s. Back then, projects were sited on rivers, etc., which would be much more difficult to do today. However, many of the newer proposed projects are either “closed-loop” in nature (i.e., don’t involve any natural bodies of water), and most of those involving existing reservoirs are chosen in order to avoid the likelihood of significant impact or opposition.

Second, the article implies that the rail technology would be unintrusive. Consider that the 50 MW demonstration project approved in Nevada has a footprint of about 100 acres for a storage capacity of something like 15 MINUTES. This includes construction of rail on a mountainside. Now, a well-sited pumped storage project typically has an energy storage of at least 6 HOURS (and often more) while occupying a far smaller footprint per kilowatt-hour of storage; furthermore, the works low in profile and largely underground. Operation is also nearly silent. Achieving a comparable energy storage duration with an ARES project would involve tearing up a large chunk of mountainside, and likely be far more visually intrusive, and not at a lower cost.

In closing, I would point out that it is a common mistake in energy journalism to put all energy storage technologies in the same basket for comparison. Nothing comes close to the cost-effectiveness of pumped storage hydro, at scale, for providing utilities with enough storage to cover their peak load periods. Siting today is much more careful than yesteryear, and there are many sites to choose from, at least in the mountainous western U.S. There are also excellent options in the east. Few in the industry would dispute this. The chief issue is the time it takes to obtain a license from FERC, and the fact that projects tend to have to be large in order to be economical.

For SHORT duration storage, which is good for moment-to-moment grid balancing, technologies like ARES might be competitive (if the costs come down, because the ARES demo project is very expensive on a per-kW and per-kWh basis). Batteries are ahead of ARES on cost today, but have the downside of short lifespans – particularly compared with pumped storage (e.g., 10 years for batteries vs. 60-75 years).

Be serious !! A train as energy storage !! It is an sign of the NAmerican decline in science, technics and culture. Using small pumped storage close to the ocean we could even provide enough storage capacity, combining wind power with energy storage using seawater reservoirs on top of steep shore cliffs.

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